The Kindle is an ebook reader designed and sold by Amazon.com, which can download new ebooks, magazines and newspapers directly from its online bookstore. Your existing library of ebooks can also be transferred to the Kindle, as long as they're in a compatible, unencrypted format and don't have any kind of digital rights management protection. The Kindle is compatible with the majority of popular computer document file types, including Mobipocket, plain text, HTML, Microsoft Word and Adobe PDF.
All ebooks and digital reading content downloaded directly from the Amazon.com online bookstore is in the .awz format. This is a proprietary format developed by Amazon.com that allows the online bookstore to apply copyright protection and an author-configurable licensing system to individual ebooks. The .awz files allow for full illustration within ebooks, and can display all forms of text formatting including interactive elements such and Internet hyperlinks. As .awz files are copyright protected, they cannot be manually transferred to or from the Kindle, although they can be sent to different devices through the Kindle's associated Amazon.com online account.
Mobipocket is a French company that popularized ebook reading and sales on computers and personal digital assistant devices. The company was bought by Amazon.com in 2005, and Mobipocket's .mobi file format was used as the basis for the Kindle's .awz format. Full text formatting, page numbering and illustration is supported by .mobi ebooks. Although the format does allow for DRM protection, the Kindle cannot display encrypted .mobi ebooks. The .mobi format itself is very closely related to the Palm Pilot's .prc digital document format, making .prc ebooks equally compatible with the Kindle.
Adobe developed its Portable Document Format in 1993 in an effort to established a standardized, cross-platform document that maintains its appearance and layout regardless of the software, hardware or operating system. PDF support was added to the Kindle in version 2.3 of its firmware, although compatibility is still considered to be experimental. Certain aspects of PDF support, such as changing the font size, are not available, so some PDF documents are unable to format correctly on the Kindle's display.
Raw, or plain, text files are fully supported by the Kindle, and have the advantage of also being broadly compatible with all types of computer systems. Text files use the .txt file extension, and have the advantage of creating very small ebook files sizes, thereby extending the capacity of the Kindle's memory. These .txt files do not support any form of text formatting, however, and have no capacity for adding a cover image or illustration to an ebook.